Thanks everyone ... XJ6, '93, 160k, automatic transmission ... engine and drive train running great, smooth, quiet, instantly responsive into and out of all gears forward and reverse EXCEPT the shift up to and down from (what I assume to be) 4th gear at 50 mph. Then I get a "growl" ... not very loud and not really a loss in performance ... just seems to have a bit of a hard time getting into and then back out of the gear, and, makes the low-key grumble/growl sound while shifting itself. I'd like to know something about it before I think about taking it in somewhere.

 

That "shift" at that speed is the torque converter "locking up", and is now getting to be a common failure item.

My first suggestion, as always, is to drain and refill the trans fluid a few times, simple to do, and this "may" just sort it out.

If, however, it has been doing this for some time, the mechanical components are probably toast. This requires a converter rebuild.

 

I may have a chance with the fluid drain and refill as the problem wasn't there in Summer '12 (first year I had the car) but came up Spring '13 (and hasn't been driven but 500 miles since). Thanks again, I'll get to work on it.

 

let us know how it goes. mine has a slight groan to it too

 

What I need to know now is ... What's the very best transmission fluid to use for the "drain and refill a couple of times"? ... to give it the best chance of improving the problem. Thanks.

 

As I said before.

Synthetic ATF. I have NO idea what your market has available, but down here the manufacturers of oils have:

"Full Synthetic multi purpose transmission fluid".
This has D3 and many, many more specs on the label/s. Includes the spec for the ZF sealed 5 speed as in X308/Merc/BMW, etc.

Our brands are:
Penrite
Nulon
LSA
All of which we sell at work in huge quantities, as apposed to "Mineral ATF" which is a very slow mover now.

Look in your local parts supplier, forget Jag, look for Synthetic ATF. The wording up there may also be different to us, as in trunk/boot, and hood/bonnet, but the meanings are the same.

If all that fails, simply use standard D3. The trans will still luv ya.

 

So ... I had the transmission fluid ('93 XJ6) as completely replaced as possible. Used "Full Synthetic Multi-Purpose" fluid. Also replaced the filter and gasket while at it. Drove around town for a week (maybe 75 miles total). Then tried the Torque Converter lock/unlock at 50mph. DRASTIC IMPROVEMENT ... absolutely no growl/rumble locking-up when accelerating through 50mph (as quiet and smooth as any of the gear changes) ... perfect. Some grumble remains on the way back down through 50mph (far less than before the fluid change, maybe 1/3 as much now, and still something I'd like to improve, but seems good enough now to drive on the highway without trouble). Figure I'll take the 80 mile one way trip to visit kids in Madison a few times and then replace the fluid once more to see if I actually have a cure or if I could use a new/rebuilt Torque Converter. Anyway, seems OK to be optimistic. Thanks again.

 

Sweet, got to luv a plan that comes together.

I would be doing another drop and fill, simply undo teh big nut on the dipstick tube, and let it run out (unless you are one of the blessed with a drain plug).

I did the X300 (same family of transmission) 6 times in 2000kms, and what a difference each drop and fill made.

Now done 50K kms in 3 years and the shifts are SMOOTH, SILENT, and unless you really concentrate you would not know its changed gear, except for the tacho drop.

Now to get the 2 S Types as good HAHA.